Does Acid Addition using a SWG add to to TDS

[smallpooldad]

Does Acid Addition using a SWG add to to TDS?

[Poolsean]

VERY little.
TDS is mostly calciums, magnesiums, metals (such as copper from algaecides, heaters, mineral purifiers, etc), and other junk.

Muriatic Acid, or hydrochloric acid, will contain a minute amount of salt but negligable for testing purposes.

What's the basis of the question?

[Poolsean]

Just thought of something else, DRY ACID, which is sodium bisulfate, WILL add TDS to a pool.

[chem geek]

Both forms of acid add to TDS, but Sean is correct that Muriatic Acid (which is Hydrochloric Acid, usually at 31.45%) adds to chloride, that is salt, while Dry Acid (which is 93.2% Sodium Bisulfate) adds to sulfate.

1 cup of Muriatic Acid (31.45% HCl) in 10,000 gallons increases TDS by 2.2 ppm while the equivalent amount of Dry Acid, which is 0.9 cups, increases TDS by 7.4 ppm of which 6.4 ppm is sulfate (the rest is sodium). The reason the sulfate (or sodium sulfate) is higher is due to its higher molecular weight.

Chloride is pretty benign until it gets in fairly high quantities. Sulfate may become a problem at some point, but I can't find any source giving a definitive level when it becomes a problem. For example, this link talks about sulfate attack on concrete (similar to pool plaster), but does not give concentrations at which problems are seen.

Richard